In recent years non-vacuum deposition techniques with a capability to prepare uniform thin films using low cost techniques such as paste coating and electro chemical deposition has gained much attention among the researchers. From among the various low cost synthesis techniques, solution based synthesis process is considered to be as a promising alternative among expensive techniques with relatively simple procedures and low initial costs for its industrializing.
Thus, there is a need to provide an effective and low cost synthesis process for producing such uniform thin films.
It is known that Copper Indium Gallium (di)Selenide (CuIn1−xGaxSe2 or CIGS where x can vary from 1, corresponding to pure copper indium selenide, to 0, corresponding to pure copper gallium selenide) is a I-III-VI2 semiconductor material, in particular a direct bandgap semiconductor useful for the manufacture of solar cells. In particular, CIGS is a tetrahedically bonded semiconductor, with the chalcopyrite crystal structure and a bandgap varying continuously with x from about 1.0 eV (for copper indium selenide) to about 1.7 eV (for copper gallium selenide). The material is a solid solution of copper indium selenide (often abbreviated “CIS”) and copper gallium selenide. [0006] CIGS is used as light absorbed material for thin-film solar cells. Device made with CIGS belong to the thin-film category of photovoltaics (PVs). Typically, because the material strongly absorbs sunlight, a much thinner film is required than other semiconductor materials. Solution phase synthesis of CIGS materials, via mechano-chemical synthesis approach are known e.g. in the reference entitled “Structural studies of mechano-chemically synthesized CuIn1−xGaxSe2 nanoparticles”.
WO 2007/065859 discloses a process for preparing organically modified layered double hydroxide, while WO 99/35185 on the other hand discloses a process for preparing organically modified layered double hydroxides (LDHs) where the organic anion is introduced into the LDH via ion exchange, carried out by suspending the LDH in water, following which the pH<4 condition is imposed externally. Further the authors describe the addition of organic anions to the suspension adjusting the pH of the solution to >8. Moreover as observed by WO 2007/065859 this process is rather complex and generally renders ionic waste stream.
WO 00/09599 on the other hand describes the preparation of LDH comprising organic anions as intercalating anions. These modified LDHs can be prepared in various ways, with use being made of the salts of divalent and trivalent metal ions, such as the chloride salts of magnesium and aluminium or sodium aluminates. The processes described in WO 00/09599 require salts which will at least partially end up in the waste stream, still an undesirable effect.
In summary, the synthesis processes described into the present state of the art, urges a strong need for a less waste recurring and faster synthesis scheme.
There is thus a need to provide a simpler and faster process for preparing innovative composite nanomaterials.
Organic photo voltaic (OPVs) offer the potential to greatly decrease the cost and availability of photovoltaic energy due to lower material and manufacturing costs. A typical organic photovoltaic device architecture uses the so called bulk hetero junction (BHJ) configuration which consists of a polymer electron donor (p-type) and fullerene-derivative electron acceptor (n-type) mixture in the active layer. A typical organic photovoltaic bulk hetero junction device includes a glass or PET layer, a poly(3,4-ethylenedioxythiophene)poly(styrenesulfonate), or PEDOT:PSS layer, which is a transparent, conductive polymer mixture of two ionomers, a donor(p-type):acceptor(n-type) layer and a metal cathode layer. Generally, the modern p-type electronic polymer may include poly(3-hexylthiophene) (P3HT) or new generation of low-bandgap conducting polymers, while until now, as the n-type material, methanofullerene phenyl-C61-butyric-acid-methyl-ester ([60]PCBM) has been almost exclusively used and some attempts have also been made with [70]PCBM. Various strategies have been tried to improve the performance of the fullerene derivative (n-type), with varying degrees of successes into: increasing the optical absorption of the formed active layers, improving its solubility with the constituent specie forming the BHJ, improving its miscibility with the p-type polymer and increasing the energy level of the Lowest Unoccupied Molecular Orbital (LUMO). In context of the LUMO “tuning” of the acceptor (n-type) molecule; it has been shown that the open circuit voltage (Voc) of the solar device is a function of the energy gap between the Highest Occupied Molecular Orbital (HOMO) in the donor and the LUMO in the acceptor. As a result, increasing the LUMO in a wide range of donors could significantly increase Voc when they are paired with e.g. P3HT and other acceptor polymers with similar properties.
However, there are drawbacks with current organic photo voltaic (OPV) technology which can be summarized as: 1). Not efficient Absorption, 2). Not enough charge separation, 3). Not enough charge transport.
There is thus a need to provide and improve hybrid composite nanomaterials to overcome at least one of the drawbacks of the prior art, such as to obtain efficient light absorption, enough charge separation and enough charge transport in OPV cells and apparatuses.